Tesla opens up Solar Roof pre-orders, answers the most important question: how much will it cost you?

Back in October of last year, Tesla unveiled a new project it had been secretly cracking away at behind the scenes: solar roof tiles. Unlike traditional solar panels that sit on top of the roof, these solar tiles would replace your roof outright — and, if all went to plan, they’d look as good as any other roof. Just… maybe a little shinier.

The first question that popped up on everyone’s mind seemed to be the same: “Cool! How much will it cost?”

Alas, that question has proven challenging to answer. Tesla has given ballpark estimates and comparison numbers, but there’s no one concrete answer that fits all homes. Different homes have different energy needs; different structures have different roofs and different challenges (chimneys, trees, etc); different states have different tax breaks.

This afternoon, pre-orders are going live ($1,000 deposit, refundable if you change your mind before signing the final contract). They can’t really expect people to pre-order without some idea of what they’ll pay in the end, so they’ve built a cost calculator that tries to crunch the numbers for your specific house.

Punch in your address and it’ll spit out a custom estimate.

Here’s what one looks like:

Tesla is tapping Google’s Project Sunroof here, which uses some 3D mapping trickery to give them a rough idea of how much roof area (square footage) you’ve got, and how much of it is actually good for solar use. That gives them a ballpark estimate for the roof cost (including materials, installation and the cost of removing your old roof), at which point they factor in the cost of a Powerwall battery. Then they wrap in offsets like local tax credits and the money saved on your electric bill to give you a final cost after 30 years.

Tesla CEO Elon Musk also shed a bit of light on how the ordering process works: Once you’ve placed your order and made your way up the waiting list, they send out an engineer who works out exactly what your roof needs. How much square footage of tile? How much of it should be solar versus non-solar?

That last bit is an interesting note: not all tiles they install will actually be solar tiles. Spots on your roof that don’t get much sun, for example, will get non-solar tiles — but they’ll look exactly the same from the street, says Elon.

The company also tightened up the timing window of various panel styles a bit: installations of the the smooth/textured glass solar panels will start this year, while the wavier Tuscan and Slate panels won’t start hitting houses until 2018 (Elon tweeted that it’d be in “about 6 months,” so it sounds like he’s aiming for sooner than later.)